Pioneer is a good stereo for the radio and self contained power but I have always had good luck with Kenwood. As long as you stick to a name brand you can't really go wrong with the head unit. Blaupunkt, Pioneer, Kenwood, Alpine, Panasonic, Sony and JVC. Just pick one that has the features you want and has the look you want.
I think the speakers and amp are the most important. I have Infinity Kappa 3 way 6.9i in mine...6 1/2 (225w) and 6x9 (330w) in the rear door I believe. I tested everything at a really cool store when I bought them where you could close the door and crank them up with your choice of amps and heads. NOTHING came close to the Kappas for crystal clear sound and crisp bass...NOTHING!!! You need a powerfull amp to push these and get the proper sound...100 RMS min. per channel.
I doubt you find them at Best Buy but I got my whole kit at Onlinecarstereo.com They have the best prices and fast shipping. They always have stuff on sale and great closeout deals.
Be carefull of the "high watt" off brand amps...they are never as advertised so go with a good name brand amp or one that you can read the customer reviews.
Good luck!